rhi: metal: Use scale from the layer we already have

...so that we do not need to call devicePixelRatio() again, which means
one less UI Thread Checker warning in Xcode.

Pick-to: 6.5
Task-number: QTBUG-97518
Change-Id: I01d54ea113788cd0b141e124a47940f5cd3efabb
Reviewed-by: Laszlo Agocs <laszlo.agocs@qt.io>
Reviewed-by: Qt CI Bot <qt_ci_bot@qt-project.org>

1 files changed, 6 insertions, 4 deletions

diff --git a/src/gui/rhi/qrhimetal.mm b/src/gui/rhi/qrhimetal.mm
index 445afa111e..7b7856ec54 100644
--- a/src/gui/rhi/qrhimetal.mm
+++ b/src/gui/rhi/qrhimetal.mm
@@ -5633,8 +5633,9 @@ bool QMetalSwapChain::createOrResize()
     int width = (int)d->layer.bounds.size.width;
     int height = (int)d->layer.bounds.size.height;
     CGSize layerSize = CGSizeMake(width, height);
-    layerSize.width *= d->layer.contentsScale;
-    layerSize.height *= d->layer.contentsScale;
+    const float scaleFactor = d->layer.contentsScale;
+    layerSize.width *= scaleFactor;
+    layerSize.height *= scaleFactor;
     d->layer.drawableSize = layerSize;
 
     m_currentPixelSize = QSizeF::fromCGSize(layerSize).toSize();
@@ -5673,12 +5674,13 @@ bool QMetalSwapChain::createOrResize()
 
     rtWrapper.setRenderPassDescriptor(m_renderPassDesc); // for the public getter in QRhiRenderTarget
     rtWrapper.d->pixelSize = pixelSize;
-    rtWrapper.d->dpr = float(window->devicePixelRatio());
+    rtWrapper.d->dpr = scaleFactor;
     rtWrapper.d->sampleCount = samples;
     rtWrapper.d->colorAttCount = 1;
     rtWrapper.d->dsAttCount = ds ? 1 : 0;
 
-    qCDebug(QRHI_LOG_INFO, "got CAMetalLayer, size %dx%d", pixelSize.width(), pixelSize.height());
+    qCDebug(QRHI_LOG_INFO, "got CAMetalLayer, pixel size %dx%d (scale %.2f)",
+            pixelSize.width(), pixelSize.height(), scaleFactor);
 
     if (samples > 1) {
         MTLTextureDescriptor *desc = [[MTLTextureDescriptor alloc] init];